To make the brown butter mayonnaise, heat the butter over medium heat until browned, then add grapeseed oil.

In a small food processor mix the egg yolks, lemon juice and salt, then gradually add the oil and butter mixture to create a thick mayonnaise. Set aside.

Prepare the crab and crayfish by placing in the freezer for about 20 minutes to put them to sleep, then spiking between the eyes with a sharp knife or metal skewer. Clean the crab and separate into 4 pieces, and divide the crayfish in half lengthways. Remove the intestinal tract from the crayfish. (You can keep the crab and crayfish whole if you wish, but I find that breaking them up makes this dish easier to share.)

Remove the intestinal tract from the prawns, keeping the shells intact. Brush the mussels if necessary.

Bring about 5 litres of water to a simmer in a large pot and add the salt, sugar, lemons, dill and white wine. Add the crab and crayfish and simmer for about 10 minutes. Add the prawns and simmer for a further 2 minutes, then add mussels for a final 2 minutes, just until the shells open. Remove all the shellfish from the pot and serve either warm or chilled with the mayonnaise, lemon wedges and crusty bread.